@angelos
 
True, most Sukhoi Su-25 use the 30mm double/dual-barrel Gryazev-Shipunov GSh-30-2 , an autocannon perhaps, but not a rotary or Gatling style autocannon.
 
But, if I can collaborate with my 2 cents, I would dare to say the artist already knew that, and actually based the gun on the rotary autocannon Gryazev-Shipunov GSh-6-30 , an actual rotary autocannon of 30mm with 6 barrels, used on the Mikoyan-Gurevich MiG-27 “Flogger” (And was actually fitted to some Sukhoi Su-25TM before being refitted with the GSh-30-2). If you take a closer look, you can actually notice that the gun of the Su-25 looks pretty similar to the GSh-6-30 (Namely at the end, compared to the GAU-8 Avenger Pinkie Pie has, which also looks similar to the real life version). So I would dare to say the artist did make both similar in regards to that so it can have a bigger impact on the picture, I personally like how the two are pretty similar in this drawing despite (Or, compared to) their “Rivalry-esque” in real life (I also like a lot of other stuff, but that’s unimportant to the current topic) , anyways, it goes well with the Friendship Is Magic show the cute plane ponies are from.
 
TL;DR? Basically the artist is right, and, at the end of the day, you choose what you want to draw anyways.
 
Good day
 
Flieger

Hey Pinkie pie The Pony Looks Large But What is Inside Body?

Su-25 is not using gatling gun.